Electric relay



May 3, 1938. J. E. CARLSON ELECTRIC RELAY Filed July 25, 1936 INVENTOR Jog n E. CARLSON mbmuav Illlllllllllll PatentedMay 3, 1938 UNITED STATES PATENZ! OFFICE ELECTRIC RELAY necticut Application July 25, 1936, Serial No. cases 4 Claims.

My invention relates to devices of the general character set forth in the Getchell Patent 1,681,851 used for protecting electrical circuits. This particular invention is directed to a device especially intended for use in an independent coil circuit or other system in which a secondary circuit is opened and closed by changes taking place in a main motor circuit.

One object is to provide a switch which is not only automatically opened upon a certain overload in the main circuit but which is automatically reset when conditions are returned to normal in the main circuit.

One object is to provide a device of this charl5 acter which can be readily inserted into and removed from terminal clips of the main and secondary circuits.

1 One object is to provide a construction of the foregoing character involving a thermostatic actuator for the switch in the secondary circuit which actuator not only opens the secondary circuit upon an overload condition in the main circuit but also closes the secondary circuit when the overload is removed.

Fig. 1 is a plan view of one form of relay embodying my invention.

Fig. 2 is a longitudinal sectional view of the same.

Fig. 3 is a transverse sectional view on the plane of the line 33 of Fig. 2.

Fig. 4 is an exploded perspective view of certain elements of the construction.

The active parts of the device are enclosed within a body or housing formed of two parts I 36 and 8 formed of insulating material and held together by cylindrical caps 9 and III which form the main terminals of the relay and are adapted to fit into the usual clips or other mounting terminals (not shown). Enclosed within the in- 40 sulating body is a heater strip II, the ends of which are suitably connected to the terminal caps 9 and I! so that this heater strip constitutes a part of the main conducting circuit of the system..

The terminals l4 and 15 of the secondary circuit switch are secured to an extension of the insulating body bymmembers l6 and I1 respectively and are adapted to engage terminal clips 50 of suitable form (not shown).

The secondary s'witeh consists of a resilient switch member l8 and a relatively stationary but -mostatic member 25 is connected to the switch member l8 by an insulating piece 23 which has a slot 24 through which the member 58 extends.

A strip 25 of thermai insulating materiai such 10 as asbestos is prefers. y interposed between the heater strip H and. t. c ermostatic strip 1'20.

When an overload. o s the main circuit the resistance of the strip 56 causes it to become heated and this increase in temperature warps is the thermostatic strip 28 which pulls the insulating member 23 so as to retract the switch mem ber I8 from the stationary contact l9 and open the secondary or independent circuit. When the conditions in the main circuit are such as to 243 permit the heater strip II to cool off, the thermostatic strip 2| resumes its normal position and closes the circuit through the members l8 and [9 of the secondary switch.

I claim:

1. An automatic relay including an insulating housing, a heater strip within the housing having main terminals, a bimetallic thermostatic member under the influence, of the heater strip, a secondary circuit switch carried by the housing 30 and having external terminals independent of the terminals of the heater strip, and insulating means of connection between the secondary switch and the thermostatic member, whereby said bimetallic member is independent of the secondary circuit.

2. In a relay, an insulating housing having cylindrical ends and an extension between the ends projecting laterally from one side of the housing, main terminal caps on the ends, a re- 40 sistance heater electrically connecting said caps within the housing, independent circuit terminals adjacent opposite ends of the lateral extension, a switch having contacts within said extension electrically connected to the respective independent circuit terminals and means actuated by an overload in the circuit through the heater for opening the circuit through said switch.

3. In a relay, an insulating housing having cylindrical ends and an extension between the ends projecting laterally from one side of the housing, main terminal caps on the ends, a resistance heater electrically connecting said caps within the housing, independent circuit ter- '56 minals adjacent opposite ends of the extension, a switch having contacts within said extension electrically connected to the respective independent circuit terminals and means for opening and closing the circuit through the switch upon increase and decrease respectively or the load in the main circuit, said means including a bimetallic strip under the influence of said heater but carrying no current and an insulating piece operatively connecting said bimetallic strip and switch.

4. An automatic relay including a housing, a lateral extension on the housing centrally there= oi, a main circuit terminal at each end of the housing, a heater in the housing connecting; the

2,1 1&097

JOHN E. cAaLsoN. 5 

